Immune Profiling to Determine Early Disease Trajectories Associated With Coronavirus Disease 2019 Mortality Rate: A Substudy from the ACTT-1 Trial.

Coronavirus disease 2019 (COVID-19) outcomes are linked to host immune responses and may be affected by antiviral therapy. We investigated antibody and cytokine responses in ACTT-1 study participants enrolled at our center. We studied serum specimens from 19 hospitalized adults with COVID-19 randomized to treatment with remdesivir or placebo. We assessed severe acute respiratory syndrome coronavirus 2 antibody responses and identified cytokine signatures, using hierarchical clustering. We identified no clear immunologic trends attributable to remdesivir treatment. Seven participants were initially seronegative at study enrollment, and all 4 deaths occurred in this group with more recent symptom onset. We identified 3 dominant cytokine signatures, demonstrating different disease trajectories.

Luciferase-assisted detection of extracellular ATP and ATP metabolites during immunogenic death of cancer cells.

The efficacy of cancer chemotherapy is enhanced by induction of sustainable anti-tumor immune responses. Such responses involve accumulation of immunogenic mediators, such as extracellular ATP and ATP metabolites, within the tumor microenvironment. Recent studies have identified nucleotide-permeable plasma membrane channels or pores that are activated as early downstream consequences of different regulated cell death pathways: pannexin-1 channels in apoptosis, MLKL pores in necroptosis, and gasdermin-family pores in pyroptosis. This chapter describes the use of highly quantitative and semi-high-throughput methods based on the ATP sensor luciferase to measure dynamic changes in extracellular ATP, ADP, and AMP in tissue/cell culture models of cancer cells during various modes of regulated cell death in response to chemotherapeutic drugs, death receptors, or metabolic perturbation.

Identification and characterization of ecto-nucleoside triphosphate diphosphohydrolase 1 (CD39) involved in regulating extracellular ATP-mediated innate immune responses in Japanese flounder (Paralichthys olivaceus).

Extracellular adenosine triphosphate (eATP), released following inflammatory stimulation or infection, is a potent signaling molecule in activating innate immune responses in fish. However, the regulation of eATP-mediated innate immunity in fish remains unknown. Ecto-nucleoside triphosphate diphosphohydrolase 1 (CD39) is a critical molecular switch for controlling the ATP levels in the extracellular space. CD39 plays a key role in regulating eATP-activated innate immune responses through the phosphohydrolysis of pro-inflammatory eATP to inactive AMP. Here, we identified and characterized a CD39 homolog (namely, poCD39) in the Japanese flounder Paralichthys olivaceus and analyzed its regulatory role in eATP-mediated innate immunity. Real-time quantitative PCR analysis revealed that poCD39 is ubiquitously present in all tested normal tissues with dominant expression in enriched Japanese flounder head kidney macrophages (HKMs). Immune challenge experiments demonstrated that poCD39 expression was upregulated by inflammatory stimulation and Edwardsiella tarda infection. Biochemical and immunofluorescence analysis revealed that poCD39 is a functional glycosylated membrane protein for the hydrolysis of eATP. Inhibition of poCD939 activity with the ecto-NTPDase inhibitor ARL 67156 resulted in increased IL-1beta gene expression and ROS production in Japanese flounder HKMs. In contrast, overexpression of poCD39 in Japanese flounder FG-9307 cells reduced eATP-induced pro-inflammatory cytokine IL-1beta gene expression. Finally, poCD39 expression was significantly induced by eATP stimulation in the HKMs, suggesting that eATP may provide a feedback mechanism for transcriptional regulation of fish CD39. Taken together, we identified and characterized a functional fish CD39 protein involved in regulating eATP-mediated innate immune responses in fish.

Innate Immune Activation by cGMP-AMP Nanoparticles Leads to Potent and Long-Acting Antiretroviral Response against HIV-1.

HIV-1 evades immune detection by the cGAS-STING cytosolic DNA-sensing pathway during acute infection. STING is a critical mediator of type I IFN production, and STING agonists such as cGMP-AMP (cGAMP) and other cyclic dinucleotides elicit potent immune and antitumor response. In this article, we show that administration of cGAMP, delivered by an ultra-pH-sensitive nanoparticle (NP; PC7A), in human PBMCs induces potent and long-acting antiretroviral response against several laboratory-adapted and clinical HIV-1 isolates. cGAMP-PC7A NP requires endocytosis for intracellular delivery and immune signaling activation. cGAMP-PC7A NP-induced protection is mediated through type I IFN signaling and requires monocytes in PBMCs. cGAMP-PC7A NPs also inhibit HIV-1 replication in HIV+ patient PBMCs after ex vivo reactivation. Because pattern recognition receptor agonists continue to show more clinical benefits than the traditional IFN therapy, our data present important evidence for potentially developing cGAMP or other STING agonists as a new class of immune-stimulating long-acting antiretroviral agents.

Evolution of the metabolome in response to selection for increased immunity in populations of Drosophila melanogaster.

We used NMR-based metabolomics to test two hypotheses-(i) there will be evolved differences in the metabolome of selected and control populations even under un-infected conditions and (ii) post infection, the metabolomes of the selected and control populations will respond differently. We selected replicate populations of Drosophila melanogaster for increased survivorship (I) against a gram-negative pathogen. We subjected the selected (I) and their control populations (S) to three different treatments: (1) infected with heat-killed bacteria (i), (2) sham infected (s), and (3) untreated (u). We performed 1D and 2D NMR experiments to identify the metabolic differences. Multivariate analysis of the metabolic profiles of the untreated (Iu and Su) flies yielded higher concentrations of lipids, organic acids, sugars, amino acids, NAD and AMP in the Iu treatment as compared to the Su treatment, showing that even in the absence of infection, the metabolome of the I and S regimes was different. In the S and I regimes, post infection/injury, concentration of metabolites directly or indirectly associated with energy related pathways (lipids, organic acids, sugars) declined while the concentration of metabolites that are probably associated with immune response (amino acids) increased. However, in most cases, the I regime flies had a higher concentration of such metabolites even under un-infected conditions. The change in the metabolite concentration upon infection/injury was not always comparable between I and S regimes (in case of lactate, alanine, leucine, lysine, threonine) indicating that the I and S regimes had evolved to respond differentially to infection and to injury.

Ecto-5'-nucleotidase/CD73 enhances endothelial barrier function and sprouting in blood but not lymphatic vasculature.

CD73/ecto-5'-nucleotidase is a key enzyme in the regulation of purinergic signaling and inflammatory reactions. It hydrolyzes extracellular AMP into adenosine, which dampens immune cell activation, and reduces leukocyte trafficking. By comparing CD73 expression and function in mononuclear and endothelial cells (ECs) of blood and lymph, we show that extracellular purines and CD73 activity have differential effects in these two vascular systems. We found that CD8-positive T lymphocytes and CD19-positive B lymphocytes in human lymph expressed high levels of CD73 and other purinergic enzymes and adenosine receptors. Soluble CD73 was less abundant in human lymph than in serum, whereas CD73 activity was higher in afferent lymphatic ECs than in blood ECs. Adenosine signaling improved barrier function and induced sprouting of human blood, but not lymphatic, ECs in vitro. Similarly, using CD73-deficient mice we found that CD73 controls only blood vascular permeability at selected lymphoid organs under physiological conditions. Thus, both vascular and lymphatic arms of the immune system synthesize the components of purinergic signaling system, but surprisingly they use CD73 differentially to control endothelial permeability and sprouting.

Development and validation of a generic fluorescent methyltransferase activity assay based on the transcreener AMP/GMP assay.

Methylation is a ubiquitous covalent modification used to control the function of diverse biomolecules including hormones, neurotransmitters, xenobiotics, proteins, nucleic acids, and lipids. Histone methyltransferases (HMTs) are currently of high interest as drug targets because of their role in epigenetic regulation; however, most HMT assay methods are either not amenable to a high-throughput screening (HTS) environment or are applicable to a limited number of enzymes. The authors developed a generic methyltransferase assay method using fluorescent immunodetection of adenosine monophosphate (AMP), which is formed from the MT reaction product S-adenosylhomocysteine in a dual-enzyme coupling step. The detection range of the assay; its suitability for HTS, including stability of reagents following dispensing and after addition to reactions; and the potential for interference from drug-like molecules was investigated. In addition, the use of the assay for measuring inhibitor potencies with peptide or intact protein substrates was examined through pilot screening with selected reference enzymes including HMT G9a. By combining a novel enzymatic coupling step with the well-characterized Transcreener AMP/GMP assay, the authors have developed a robust HTS assay for HMTs that should be broadly applicable to other types of methyltransferases as well.

New mechanism of oral immunity to mucosal candidiasis in hyper-IgE syndrome.

Oropharyngeal candidiasis (OPC, thrush) is an opportunistic infection caused by the commensal fungus Candida albicans. An understanding of immunity to Candida has recently begun to unfold with the identification of fungal pattern-recognition receptors such as C-type lectin receptors, which trigger protective T-helper (Th)17 responses in the mucosa. Hyper-IgE syndrome (HIES/Job's syndrome) is a rare congenital immunodeficiency characterized by dominant-negative mutations in signal transducer and activator of transcription 3, which is downstream of the Th17-inductive cytokines interleukin (IL)-6 and IL-23, and hence patients with HIES exhibit dramatic Th17 deficits. HIES patients develop oral and mucocutaneous candidiasis, supporting a protective role for Th17 cells in immunity to OPC. However, the Th17-dependent mechanisms of antifungal immunity in OPC are still poorly defined. An often unappreciated aspect of oral immunity is saliva, which is rich in antimicrobial proteins (AMPs) and exerts direct antifungal activity. In this study, we show that HIES patients show significant impairment in salivary AMPs, including ß-defensin 2 and Histatins. This tightly correlates with reduced candidacidal activity of saliva and concomitantly elevated colonization with Candida. Moreover, IL-17 induces histatins in cultured salivary gland cells. This is the first demonstration that HIES is associated with defective salivary activity, and provides a mechanism for the severe susceptibility of these patients to OPC.

Bronchial hyperresponsiveness to methacholine and adenosine 5'-monophosphate, and the presence and degree of atopy in young children with asthma.

BACKGROUND: Bronchial hyperresponsiveness (BHR) is a characteristic feature of asthma, and is usually measured by bronchial challenges using direct or indirect stimuli. The relationship between atopy and BHR remains to be clarified, particularly in a population selected for asthma. Furthermore, data for young children are limited, although asthma frequently occurs in early childhood. OBJECTIVE: The aim of this study was to investigate methacholine (direct stimulus) and adenosine 5'-monophosphate (AMP) (indirect stimulus) responsiveness according to the presence and degree of atopy in young children with asthma. METHODS: A retrospective analysis of data from 122 preschool children (median age [range]: 5.3 years [4.0-6.8]) presenting with the diagnosis of asthma was performed. These children were characterized by skin-prick tests (SPTs) and bronchial challenges with methacholine and AMP, using a modified auscultation method. The end-point concentration, resulting in audible wheezing and/or oxygen desaturation, was determined for each challenge. Atopy was defined by at least one positive reaction to SPTs, and its degree was assessed using serum total IgE levels, number of positive SPTs, and atopic scores (sum of graded weal size). RESULTS: Atopic patients (n=97) had a significantly lower AMP end-point concentration than non-atopic patients (n=25), whereas the methacholine end-point concentration was not different between the two groups. Among the atopic patients, there was no association between the methacholine end-point concentration and any of the atopy parameters. By contrast, a significant association was found between the AMP end-point concentration and the degree of atopy reflected in serum total IgE and atopic scores (χ² test for trend, P=0.001, 0.003, respectively). CONCLUSION AND CLINICAL RELEVANCE: Young children with atopic asthma had a significantly greater AMP responsiveness than those with non-atopic asthma, whereas methacholine responsiveness was not significantly different between the two groups. The degree of atopy appeared to be an important factor in AMP responsiveness, but not in methacholine responsiveness, and thus might be a marker of airway inflammation in asthma.

Characterization of a rabbit polyclonal antibody against threonine-AMPylation.

An antibody against the posttranslational modification AMPylation was produced using a peptide corresponding to human Rac1 switch I region with AMPylated threonine-35 residue as an antigen. The resulting rabbit antiserum was tested for its abilities to recognize AMPylated proteins by western blot and immunoprecipitation. The antiserum is highly specific for threonine-AMPylated proteins and weakly recognizes tyrosine-AMPylated proteins. Depletion of serum with modified protein abolished its activity against tyrosine-AMPylated proteins. The antiserum also recognized native proteins with modification in an immunoprecipitation experiment. Interactions of the antiserum could be inhibited by competition with AMP but not with GMP or UMP. This antiserum had potential utility for the identification of unknown AMPylated proteins.

Fluoxetine treatment to rats modifies serotonin transporter and cAMP in lymphocytes, CD4+ and CD8+ subpopulations and interleukins 2 and 4.

Several lines of evidences indicate that antidepressants produce various immunomodulatory effects. Fluoxetine, an antidepressant and selective serotonin reuptake inhibitor, modulates immune cells in vitro. To explore the in vivo influence of fluoxetine on lymphocytes, male Sprague-Dawley rats were treated daily, 10 mg/kg, or with saline solution for 1, 2 and 3 weeks. The presence of serotonin transporter in CD3+, CD4+ and CD8+ subpopulations of T lymphocytes was determined by immunofluorescence. Serotonin transporter was also labeled with [(3)H]paroxetine, specific binding defined with imipramine. Plasma levels of pro-inflammatory interleukin 2 (IL-2), and anti-inflammatory interleukin 4 (IL-4), were measured by ELISA; and cAMP concentration by radioimmunoassay. Fluoxetine significantly increased the number of lymphocytes expressing serotonin transporter and elevated the binding of [(3)H]paroxetine. The percentage of CD4+ cells decreased, that of CD8+ increased, and CD3+ did not change. The ratio CD4+/CD8+ was significantly lowered. Fluoxetine administration elevated the levels of IL-4 at 1, 2 and 3 weeks; and of IL-2, at 2 and 3 weeks. IL-4/IL-2 ratio was significantly increased in fluoxetine group respecting the controls and was similar during the 3 weeks of treatment. Fluoxetine produced a significant decrease in cAMP concentrations in lymphocytes, probably by secondary activation of serotonin receptors. Treatment with fluoxetine modified immune parameters in plasma and lymphocytes of rats, which might be relevant for its systemic therapeutic action as an antidepressant.

Antibodies as pharmacologic tools for studies on the regulation of energy balance.

OBJECTIVE: Active immunization in rats may serve several purposes: the production of a disease-like phenotype, the generation of pharmacologic tools, and the development of clinically useful therapies. We selected the melanocortin-4 receptor (MC4R) as a target because its blockade could provide a treatment for anorexia and cachexia. METHODS: We used a sequence of the N-terminal (NT) domain of the MC4R as an antigen. Rats immunized against the NT peptide produced specific MC4R antibodies (Abs) that were purified and characterized in vitro and in vivo. RESULTS: The Abs acted as inverse agonists and reduced under basal conditions the production of cyclic adenosine monophosphate in HEK-293 cells expressing the human MC4R. Rats immunized against the NT peptide developed a phenotype consistent with hypothalamic MC4R blockade, i.e., increased food intake and body weight, liver and fat-pad weights, hepatic steatosis, and increased plasma triacylglycerols. With a high-fat diet, plasma insulin levels were significantly increased. In separate experiments an increase in food intake was observed after injection of purified MC4R Abs into the third ventricle. When lipopolysaccharide was administered in NT-immunized rats the reduction of food intake was partly prevented in this model of cytokine-induced anorexia. CONCLUSION: Our results show that active immunization of rats against the MC4R resulted in the generation of specific Abs that stimulated food intake by acting as inverse agonists of the hypothalamic MC4R. Pharmacologically active monoclonal MC4R Abs could be the starting point for the development of novel treatments for patients with anorexia or cachexia.

Effect of A2B adenosine receptor gene ablation on proinflammatory adenosine signaling in mast cells.

Pharmacological studies suggest that A(2B) adenosine receptors mediate proinflammatory effects of adenosine in human mast cells in part by up-regulating production of Th2 cytokines and angiogenic factors. This concept has been recently challenged by the finding that mast cells cultured from bone marrow-derived mast cells (BMMCs) of A(2B) knockout mice display an enhanced degranulation in response to FcepsilonRI stimulation. This finding was interpreted as evidence of anti-inflammatory functions of A(2B) receptors and it was suggested that antagonists with inverse agonist activity could promote activation of mast cells. In this report, we demonstrate that genetic ablation of the A(2B) receptor protein has two distinct effects on BMMCs, one is the previously reported enhancement of Ag-induced degranulation, which is unrelated to adenosine signaling; the other is the loss of adenosine signaling via this receptor subtype that up-regulates IL-13 and vascular endothelial growth factor secretion. Genetic ablation of A(2B) receptors had no effect on A(3) adenosine receptor-dependent potentiation of Ag-induced degranulation in mouse BMMCs, but abrogated A(2B) adenosine receptor-dependent stimulation of IL-13 and vascular endothelial growth factor secretion. Adenosine receptor antagonists MRS1706 and DPCPX with known inverse agonist activity at the A(2B) subtype inhibited IL-13 secretion induced by the adenosine analog NECA, but did not mimic the enhanced Ag-induced degranulation observed in A(2B) knockout BMMCs. Thus, our study confirmed the proinflammatory role of adenosine signaling via A(2B) receptors and the anti-inflammatory actions of A(2B) antagonists in mouse BMMCs.

CD73-generated adenosine restricts lymphocyte migration into draining lymph nodes.

After an inflammatory stimulus, lymphocyte migration into draining lymph nodes increases dramatically to facilitate the encounter of naive T cells with Ag-loaded dendritic cells. In this study, we show that CD73 (ecto-5'-nucleotidase) plays an important role in regulating this process. CD73 produces adenosine from AMP and is expressed on high endothelial venules (HEV) and subsets of lymphocytes. Cd73(-/-) mice have normal sized lymphoid organs in the steady state, but approximately 1.5-fold larger draining lymph nodes and 2.5-fold increased rates of L-selectin-dependent lymphocyte migration from the blood through HEV compared with wild-type mice 24 h after LPS administration. Migration rates of cd73(+/+) and cd73(-/-) lymphocytes into lymph nodes of wild-type mice are equal, suggesting that it is CD73 on HEV that regulates lymphocyte migration into draining lymph nodes. The A(2B) receptor is a likely target of CD73-generated adenosine, because it is the only adenosine receptor expressed on the HEV-like cell line KOP2.16 and it is up-regulated by TNF-alpha. Furthermore, increased lymphocyte migration into draining lymph nodes of cd73(-/-) mice is largely normalized by pretreatment with the selective A(2B) receptor agonist BAY 60-6583. Adenosine receptor signaling to restrict lymphocyte migration across HEV may be an important mechanism to control the magnitude of an inflammatory response.

Bronchial responsiveness to methacholine and adenosine 5'-monophosphate in young children with asthma: their relationship with blood eosinophils and serum eosinophil cationic protein.

BACKGROUND: Bronchial hyperresponsiveness is a characteristic feature of asthma, and is usually measured by bronchial challenges using direct or indirect stimuli. Blood eosinophil numbers and serum levels of eosinophil cationic protein (ECP) are considered as indirect measures of airway inflammation in asthma. The aim of this study was to investigate whether bronchial responsiveness to adenosine 5'-monophosphate (AMP) is more closely associated with blood eosinophil markers, compared with that to methacholine, in young children with asthma. METHODS: Methacholine and AMP bronchial challenges were performed in 4- to 6-year-old children with asthma (n = 77) and in healthy controls (n = 32), using a modified auscultation method. The end-point was defined as the appearance of wheezing and/or oxygen desaturation. The peripheral blood eosinophil counts and serum ECP concentrations were determined in each subject. RESULTS: A positive response to methacholine (end-point concentration < or =8mg/ml) and to AMP (end-point concentration < or =200 mg/ml) was observed in 74 (96.1%) and 66 asthmatic children (85.7%), respectively. A majority of controls was unresponsive to both challenges. In the asthma group, there was no significant correlation between methacholine end-point concentration and the eosinophil counts (r = -0.111, P = 0.337) or serum ECP levels (r = -0.126, P = 0.274). In contrast, AMP end-point concentration correlated significantly with the eosinophil counts (r = -0.372, P = 0.001) and with serum ECP levels (r = -0.371, P = 0.001). CONCLUSIONS: Our results suggest that bronchial responsiveness to AMP is more closely related to airway inflammation, compared with that to methacholine, and support the potential usefulness of AMP challenges in detecting inflammatory changes in young children with asthma.

Addition of fexofenadine to inhaled corticosteroid therapy to reduce inflammatory biomarkers in atopic asthma.

BACKGROUND: We previously showed that H1-antihistamines may shift the PC20 (provocation concentration that caused a decrease in forced expiratory volume in 1 second of 20%) threshold to adenosine monophosphate (AMP) challenge but may paradoxically prolong recovery. OBJECTIVES: To measure AMP recovery using a constant predetermined AMP PC20 and to evaluate whether fexofenadine use confers add-on effects to treatment with either fluticasone propionate alone or combined fluticasone propionate-salmeterol. METHODS: Fourteen atopic patients with mild-to-moderate asthma (forced expiratory volume in 1 second of 76%) completed a double-blind, randomized, crossover study consisting of 3-week treatment blocks of either fluticasone propionate-salmeterol, 250 microg twice daily, or fluticasone propionate alone, 250 microg twice daily, in conjunction with either fexofenadine, 180 mg once daily, or matched placebo. Recovery after a predetermined AMP PC20 challenge was measured (primary outcome), along with exhaled nitric oxide levels, plasma eosinophil cationic protein levels, peripheral eosinophil counts, pulmonary function, diary card outcomes, and quality of life (all secondary outcomes). RESULTS: There were no differences in any of the primary or secondary outcomes when fexofenadine was added to treatment with either fluticasone propionate-salmeterol or fluticasone propionate alone. The mean AMP recovery time was 25.0 vs 23.4 minutes for fexofenadine and placebo, respectively, as add-on to fluticasone-salmeterol and 22.5 vs 23.9 minutes, respectively, as add-on to fluticasone alone. CONCLUSION: Fexofenadine did not affect recovery to a fixed dose of AMP challenge or any other surrogate inflammatory markers when given as add-on therapy to corticosteroid-treatedatopic asthmatic patients.

Effect of histamine and adenosine 5'-monophosphate provocation on sputum neutrophils and related mediators in atopic patients.

BACKGROUND: Airway hyperresponsiveness and inflammation can be noninvasively studied by bronchial provocation using direct (histamine) or indirect (adenosine 5'-monophosphate [AMP]) stimuli and induced sputum. OBJECTIVE: To report on the immediate effects of histamine and AMP challenge on induced sputum neutrophil counts and related mediator levels. METHODS: We performed a single-masked, randomized, placebo-controlled, 3-way, crossover, methodological study in 14 atopic patients (median age, 25 years; 8 males; mean +/- SD forced expiratory volume in 1 second, 99% +/- 5%) without anti-inflammatory medication use. At baseline, sputum induction was performed. Bronchial challenges with AMP, histamine, or placebo were performed 48 hours later. Thirty minutes after challenge, sputum induction was performed again. Challenge periods in each patient were separated by more than 2 weeks. Sputum cells and the mediators leukotriene B4, interleukin 8, myeloperoxidase, and albumin were quantified. RESULTS: Comparing median challenge-induced relative changes in cells and mediators, neither histamine nor AMP challenge altered the induced sputum neutrophil counts (histamine, 2.7%; AMP, 2.95%; placebo, -2%; P > .07 for all), interleukin 8 levels (histamine, 2.4 ng/mL; AMP, -3.8 ng/mL; placebo, -0.2 ng/mL; P > .06), leukotriene B4 levels (histamine, -4.8 pg/mL; AMP, 3 pg/mL; placebo, 6 pg/mL; P > .08), or myeloperoxidase levels (histamine, 0.16 microg/mL; AMP, 0 microg/mL; placebo, -0.03 microg/mL; P > .07). Sputum albumin levels were increased after histamine challenge compared with AMP and placebo challenge (P < .01 for both). CONCLUSIONS: Histamine and AMP provocation have no major effects on induced neutrophil counts and related mediator levels in atopic patients, whereas histamine challenge induces plasma leakage. Potential interactions of noninvasive methods to evaluate airway reactivity and inflammation should be carefully considered.